Events
On This Day - September 20
| 1917 | K17 | Completed |
| 1939 | Wilk (Dutch) | Arrived in Britain and entered the harbour of Rosyth under the escort of the British destroyer HMS Sturdy |
| 1941 | P222 | Launched |
| 1941 | Thule (P325) | Laid Down |
| 1941 | Tudor (P326) | Laid Down |
| 1942 | Unruffled (P46) | HMS Unruffled torpedoes and sinks the Vichy-French merchant Liberia about 7 nautical miles north-east of Mahdia, Tunisia. |
| 1942 | P614 | HMS P-614 attacks the German submarine U-408 with torpedoes in the Arctic Ocean. All torpedoes miss. The crew thought they had sunk the target and the skipper (Lt. Beckley) even received a DSO for the sinking. |
| 1942 | Traveller (N48) | HMS Traveller ended her 3rd war patrol at Beirut |
| 1942 | Unseen (P51) | HMS Unseen departed Portsmouth for Gibraltar. Her first lieutenant had had a wisdom tooth removed shortly before departure and began to bleed from the wound. The bleeding could not be stopped and Unseen was forced to divert to Falmouth in order to obtain medical assistance at the local hospital. |
| 1942 | Unseen (P51) | Captain Crawford awoke and went to the bridge where he saw a shape which the officer of the watch reported to him as an island. Crawford was "not impressed", as he knew there were no islands in the vicinity and sounded the night alarm. With engines stopped, they were able to hear the engines of a destroyer. Unseen was forced hurriedly to dive to avoid the destroyer, but it was clear she had already been spotted by the enemy. She was attacked with depth charges and began to sink fast. The crew managed to stop her at about 345 feet. The safe diving depth for the submarine was 200 feet according to standing instructions. The Q-tank was damaged, her navigational lights were blown off, a mass of caulking from the bulkheads was lost and damage was suffered to electrical equipment. Unseen underwent repairs upon her return to Gibraltar. To celebrate their escape, Crawford ordered a diving helmet to be sewn on to Unseen's Jolly Roger when they returned to Malta the following month. |
| 1943 | Sirdar (P226) | Completed |
| 1944 | Sceptre (P215) | HMS Sceptre torpedoes and sinks the Norwegian merchant Vela and the German minesweeper M 132 about 11 nautical miles west-south-west of Norway. |
| 1945 | L26 | HMS L-26 scuttled Halifax approaches |
| 1945 | Achates (P433) | Launched |
